Vitamin C and Colds: The Bottom Line

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Hello. I'm Dr. Sandra Fryhofer. Welcome to Medicine Matters. The topic: a controversy that has gone on for more than 70 years. Does vitamin C work for preventing and treating colds? A study was recently published in the Cochrane Database of Systematic Reviews.^[1] Here's why it matters.

The common cold is common. There are over 200 different viruses that can cause them. It's a major cause of missing both work and school and the leading cause of acute morbidity and doctor visits in high-income countries. And because colds are caused by viruses, antibiotics don't help, but that does not stop the quest for a cure. Using vitamin C became particularly popular in the 1970s, when Nobel Laureate Linus Pauling gave vitamin C for colds his seal of approval, on the basis of early placebo-controlled trials.^[2]

That was then. Now, in this new review, 72 studies were analyzed. Only those using supplement doses of 200 mg or higher were included. The conclusion:

• First, for preventing colds -- 20 trials with more than 11,000 patients showed that for most people, vitamin C didn't help much. It reduced colds, but only by 3%. For those under high physical stress -- marathon runners, skiers, and soldiers doing sub-Arctic exercise -- the results were dramatically different. The extra vitamin C in these patients cut colds in half.

• Next, duration of symptoms -- nearly 10,000 colds and 31 studies. The conclusions: for adults, an 8% reduction in duration of cold symptoms and nearly twice that for kids, a 14% reduction.

• Finally, for severity of cold symptoms -- in kids, doses of 1-2 g daily seemed to help.

The bottom line: More randomized controlled trials are needed. But on the basis of the data so far, vitamin C doesn't do much to keep you from getting a cold unless you're seriously stressed.

On the other hand, it's cheap and relatively safe, although a recent study says it may increase risk for kidney stones.^[3] And it does seem to help a little with how long your cold lasts and how bad it is.

What are you going to tell your patients?

For Medicine Matters, I'm Dr. Sandra Fryhofer.

Cite this: Vitamin C and Colds: The Bottom Line - Medscape - Mar 20, 2014.

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